1. Field of the Invention
The present invention relates to an improvement of a radial ball bearing used to support a shaft such as a rear shaft in a motor vehicle, for example, on which both radial loads and axial loads act.
2. Prior Art
Double row angular contact ball bearings have conventionally been used for rear shaft support in a motor vehicle and similar applications where it is necessary to support a shaft on which both radial loads and axial loads act.
A conventional double row angular contact ball bearing for supporting a rear shaft of a motor vehicle is shown in FIG. 1. As shown in FIG. 1, an outer ring 1 of the bearing has two raceway grooves 2 on its inner periphery. Between the raceway grooves is formed a shoulder 3. Similarly, an inner ring 6, indicated by a dotted line, of the bearing also has two raceway grooves 7 on its outer periphery in positions opposite to the other raceway grooves 2. Balls 5 are provided between the raceway grooves 2 and 7 of the outer and inner rings 1 and 6 such that the balls 5 can rotate freely. When the motor vehicle is advancing straight or is stopped, the bearing receives a radial load in the vicinity of the intersection of the raceway groove 2 and the direction of a load initially designed to act on the ball 5 at the time of assemblage of the bearing. During cornering or turning of the motor vehicle, the direction of the load acting on the ball 5 moves. As a result, a contact angle increases, and the load is received on a side surface 2a of the raceway groove 2.
However, when the conventional double row angular contact ball bearing receives a large axial load, an ellipse of contact produced between the ball 5 and the raceway groove 2 of the outer ring 1 overlaps an edge 3a formed by the raceway groove 2 and the shoulder 3. If the shoulder 3 is provided with a chamfer 4, as shown in FIG. 2, the ellipse of contact will overlap an edge 4a formed by the raceway groove 2 and the chamfer 4. An edge load is thus produced to act on the ball 5 and the edge 3a or 4a, so that the ball 5 and the edge 3a or 4a are dented. The dents will cause problems such as flaking of surfaces of the bearing rings 1 and 6 and balls 5, generation of abnormal noise, etc.
A solution to these problems is to extend the shoulder 3 inwards in the radial direction to increase the depth of the raceway groove 2 so that the ellipse of contact resulting from an axial load does not overlap the edge 3a or 4a. In this case, however, there is another problem, as follows.
Generally, the raceway groove is provided with a finishing allowance uniform in the radial directions, as shown in FIG. 3. Nevertheless, a finish machining is performed only in one direction. Therefore, a substantial allowance A2 near the side portions 2a of the raceway groove 2 becomes significantly greater than that A1 at the deepest point in the raceway groove 2. As a result, the finish machining is extremely time-consuming, and production costs increase.